This invention relates to a process for regenerating a moisture laden drying cartridge as well as to a drying apparatus including means for regenerating a moisture laden drying cartridge.
Drying cartridges are utilized to prepare drying air for drying synthetic plastics, which may be in the form of granulates and powders. The drying air is first passed through the material to be dried, whereby the drying air takes up moisture from the material. Subsequently, this air laden with moisture is passed through the drying cartridge which removes the moisture from the drying air. Thereafter, the drying air passes again to the material to be dried. This drying process is continued for so long until the drying cartridge can hardly remove any more moisture from the drying air. In continuously operating processes several, usually two to four, drying cartridges are used, one of which is always being regenerated. Thereby, a sufficient number of drying cartridges are always available. In discontinuously operating systems only one drying cartridge is used, which can be used for so long until the dew point has a correspondingly high temperature and only a little more moisture can be removed from the drying air. Then, this drying cartridge must be regenerated. In the regeneration, atmospheric air is heated and conducted through the cartridge to be regenerated, whereby the heated air picks up the moisture from the cartridge to be regenerated. The regeneration air is hereby warmed in order to be able to pick up the moisture as rapidly as possible. After passage through the cartridge to be regenerated, the moisture laden regeneration air is exhausted. In this known process, atmospheric air is continually drawn in from outside, heated before entry into the cartridge to be regenerated, and exhausted again after passage through the cartridge. The exhausted air contains a large amount of energy which is exhausted unused. In addition, significant amounts of energy must be utilized to heat the atmospheric air in order to warm the continuously flowing cool atmospheric air to the desired temperature.
As a rule, the cartridge to be regenerated must be cooled after regeneration before it can be used again to dry the material For this purpose in the known process the heating device is shut off and only cool atmospheric air is thereafter conducted through the dried cartridge. This atmospheric air partially remoistens the cartridge so that the degree of effectiveness of the apparatus which operates according to this process is detrimentally affected.